JP3427501B2 - Imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device using a solid-state image pickup element, and more particularly to an image pickup device for correcting a ratio of tristimulus values (RGB) corresponding to red, green and blue in accordance with an aperture value. Regarding

[0002]

2. Description of the Related Art Conventionally, CCD elements (charge transfer elements), M
2. Description of the Related Art There is known an imaging device that converts an optical image into an image signal by using an imaging device such as an OS device (metal oxide semiconductor device).

Recently, in such an image pickup apparatus, the image pickup element is downsized and the number of pixels is increased.
The aperture ratio of the image pickup element tends to decrease, and the S / N ratio of the image signal tends to decrease.

Therefore, in order to improve the S / N ratio of the image signal, an image pickup device as shown in FIG. 5 has been developed. In FIG. 5, on the surface of the image sensor 1, a light receiving portion 1a that converts light into electric charges and a transfer portion 1b that transfers the electric charges generated in the light receiving portion 1a are formed. Further, on the resin layer of the image sensor 1, an on-chip microlens 2 having a condenser lens formed corresponding to the light receiving portion 1a is arranged.

In this image pickup device 1, since the on-chip microlens 2 is arranged, the light incident on the transfer portion 1b is condensed on the light receiving portion 1a, and the amount of light received by the light receiving portion 1a increases. Therefore, the photoelectrically converted signal level increases, and the imaging device can output an image signal with a high S / N ratio.

FIG. 6 is a diagram showing an electronic still camera to which this type of image pickup device is applied. In the figure, a diaphragm 4 and a mirror 5 are arranged on the optical axis of the photographing lens 3, and an image pickup device 1 is arranged on the image plane of the photographing lens 3. The above-described on-chip microlens 2 is formed on the light receiving surface of the image pickup device 1.

Of the outputs corresponding to the three stimulus values of the image pickup device 1 (hereinafter referred to as “R output”, “G output”, and “B output”), G
The output is directly connected to the signal processing unit 7a, and the R output and the B output are connected to the signal processing unit 7a via the variable gain amplifiers 6a and 6b, respectively. A recording unit 7 that records an image signal is connected to the output terminal of the signal processing unit 7a.

A photometric section 8a for measuring the brightness of the subject is arranged at a position where the reflected light of the mirror 5 is irradiated.
The exposure calculation unit 8 is connected to the output terminal of the photometry unit 8a, and the aperture 4 and the control terminal of the image sensor 1 are individually connected to the output terminal of the exposure calculation unit 8.

On the other hand, a white balance control unit 9 is connected to the control terminals of the variable gain amplifiers 6a and 6b, and the white balance control unit 9 has a color measurement unit 9a for measuring the color of ambient light.
Are connected.

The control output of the control unit 10 is given to the taking lens 3, the image pickup device 1, the signal processing unit 7a, the recording unit 7, the exposure calculation unit 8 and the white balance control unit 9. A release button 10a is connected to the control unit 10.

In the electronic still camera having such a structure,
When the release button 10a is pressed halfway, the exposure calculation unit 8
The photometric value of the subject brightness by the photometric unit 8a is taken in, and an appropriate aperture value and exposure period are calculated.

Further, the white balance control section 9 takes in the colorimetric value of the ambient light by the colorimetric section 9a, and according to the ratio of the tristimulus values (RGB) of the ambient light, the variable gain amplifier 6a,
Control the gain of 6b.

In this state, when the release button 10a is fully pressed, the mirror 5 jumps up, and the exposure calculation section 8 adjusts the diaphragm 4 to a proper diaphragm value. The light quantity of the incident light from the taking lens 3 is limited by the diaphragm 4, and an optical image is formed on the light receiving surface of the image sensor 1. The image pickup device 1 increases the light receiving efficiency by the on-chip microlens 2 and outputs an image signal having a high S / N ratio.

This image signal is supplied to the variable gain amplifiers 6a and 6a.
The white balance is adjusted by b, and the signal processing unit 7a
Then, the gamma correction, the knee correction, the gain adjustment, and the like are performed, and the result is recorded in the recording unit 7.

[0015]

However, the conventional image pickup device 1 has a problem that the ratio of the RGB output changes according to the aperture value due to the influence of the axial chromatic aberration of the on-chip microlens 2 and the like. . For example, as shown in FIG. 7, on the open side of the diaphragm 4, there is a problem that the ratio of R output to G output becomes large and the image becomes reddish.

Particularly, when the white balance is manually selected by the photographer, the white balance is often set to the marginal limit, and the R value is set at the maximum aperture.
There was a high possibility that the ratio of GB output would change, resulting in an unnatural white balance.

As described above, since the RGB output ratio changes depending on the aperture value setting, it is difficult to accurately reproduce the hue of the subject. Therefore, it is an object of the present invention to provide an image pickup apparatus that can output an image signal with an accurate hue even if the aperture value changes.

[0018]

According to a first aspect of the present invention, there is provided optical means (21, 22) for forming an optical image of a subject.
And an aperture means (22) having an opening through which an incident light beam from the optical means passes and adjusting the aperture value by changing the diameter of the opening, and an image is formed via the optical means and the aperture means. An image pickup means (24) for converting the obtained optical image into an image signal, and an on-chip microlens (25) arranged on the light receiving side of the image pickup means and having a condenser lens formed corresponding to the pixel of the image pickup means. In the image pickup device including the color correction means (26a, 26b, 30), which takes in the aperture value of the aperture means and corrects the ratio of the color stimulus value of the image signal converted by the image pickup means in accordance with the aperture value. , 40a, 40b, 4
1) is provided.

Further, the invention according to claim 1 is characterized in that the color correction means decreases the stimulus value corresponding to red as the diameter of the opening of the diaphragm means increases.

On the other hand, the invention according to claim 2 is characterized in that the color correction means decreases the stimulus value corresponding to blue as the diameter of the opening of the diaphragm means increases.

The invention described in claim 3 is the same as claim 1 or
The image pickup device according to claim 2, wherein white balance adjusting means (31, 31a, 27a, 27) for adjusting white balance of the image signal converted by the image pickup means.
b), and the color correction means (40a, 40b, 41) are
It is characterized in that the amount of white balance adjustment by the white balance adjusting means is corrected. According to the invention described in claims 4 and 5 , the optical means for forming an optical image of the subject, the light flux changing means for changing the characteristic of the light flux passing through the optical means, and the optical means and the light flux changing means are connected. Image pickup means for converting an optical image formed into an image signal, and a light receiving side of the image pickup means
The condensing lens is arranged corresponding to the pixel of the image pickup means.
Image pickup device having on-chip microlens
The color correction means corrects the ratio of the color stimulus values of the image signal converted by the imaging means in response to the change in the characteristics of the light flux in the light flux changing means. Claim 4
The color correction means follows the increase in the diameter of the luminous flux by the luminous flux changing means.
Therefore, it is characterized by reducing the stimulus value corresponding to red
To do. On the other hand, the color correction means of claim 5 is the light flux changing means.
As the diameter of luminous flux increases,
It is characterized by decreasing.

[0022]

In the image pickup apparatus of the first aspect, the amount of light incident from the optical means is limited by the diaphragm means, and an optical image is formed on the image pickup element through the on-chip microlens. The image pickup means photoelectrically converts this optical image and outputs an image signal.

The ratio of the color stimulus values of the image signal depends on the cause such as the axial chromatic aberration of the on-chip microlens.
It changes according to the aperture value. The color correction unit takes in the aperture value adjusted by the aperture unit, and corrects the ratio of the color stimulus value of the image signal photoelectrically converted by the image sensor by the correction amount determined corresponding to this aperture value.

Therefore, it is possible to cancel the fluctuation of the stimulus value due to the aperture value, and an image signal having an accurate hue is output. Further, in the image pickup apparatus according to the first aspect, the stimulus value corresponding to the red color of the image signal is decreased in response to the increase in the diameter of the opening of the diaphragm means.

As shown in FIG. 7, since the red stimulus value remarkably increases on the wide aperture side, by reducing the stimulus value corresponding to red, the variation in hue is effectively suppressed, and the hue An accurate image signal is output.

On the other hand, in the image pickup device according to the second aspect , the stimulus value corresponding to the blue color of the image signal is decreased in response to the increase in the diameter of the opening of the diaphragm means. As shown in FIG. 7, since the blue stimulus value increases on the open aperture side, by reducing the stimulus value corresponding to blue, the variation in hue is suppressed,
An image signal with an accurate hue can be output.

In the image pickup device of claim 3 , the color correction means is
The adjustment amount of the white balance adjusting means is corrected according to the aperture value. Since the ratio of the stimulus values of the image signal is adjusted by the adjustment amount corrected in this way, the white balance is adjusted and the hue variation due to the aperture value is suppressed, and an accurate image signal of the hue is output. In the image pickup device according to the fourth and fifth aspects , after the characteristic of the light flux passing through the optical means is changed by the light flux changing means, an optical image is formed on the image pickup means. The image pickup means photoelectrically converts this optical image and outputs an image signal. The ratio of the color stimulus values of the image signal changes according to the change in the characteristics of the light flux by the light flux changing means. The color correction means takes in the characteristic change of the light flux in the light flux changing means, and corrects the ratio of the color stimulus values of the image signal by the correction amount determined corresponding to the characteristic change of the light flux. Sanawa
In the image pickup device according to claim 4, the luminous flux by the luminous flux changing means is used.
The stimulus value corresponding to red decreases as the diameter of
It On the other hand, in the image pickup apparatus according to claim 5, the light flux changing means is used.
The stimulus value corresponding to blue decreases as the diameter of the luminous flux increases.
Reduce. Therefore, it is possible to cancel the fluctuation of the stimulus value due to the change of the characteristic of the light flux, and the image signal of the correct hue is output.

[0028]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing an embodiment corresponding to claims 1, 2 , 4, and 5 .

In the figure, a diaphragm 22 and a mirror 23 are arranged on the optical axis of the taking lens 21.
The image pickup device 24 is arranged on the image forming plane. An on-chip microlens 25 is formed on the light receiving surface of the image pickup device 24.

The G output of the image pickup device 24 is supplied to the signal processing unit 28.
a is directly connected to a and the R output is a variable gain amplifier 26.
The signal processing unit 28a is connected via a and 27a. Further, the B output is the variable gain amplifiers 26b and 27.
It is connected to the signal processing unit 28a via b. A recording unit 28 that records an image signal is connected to the output terminal of the signal processing unit 28a.

Further, a photometric section 29a for photometrically measuring the subject brightness is arranged at a position where the reflected light of the mirror 23 is irradiated. The exposure calculation unit 29 is connected to the output terminal of the photometry unit 29 a, and the aperture calculation unit 29 is connected to the output terminal of the exposure calculation unit 29.
The control terminals of the image sensor 24 and the color correction unit 30 are individually connected.

The output terminal of the color correction section 30 is connected to the control terminals of the variable gain amplifiers 26a and 26b. on the other hand,
The white balance control unit 31 is connected to the control terminals of the variable gain amplifiers 27a and 27b, and the white balance control unit 31 is connected to the color measurement unit 31a that measures the ambient light.

A control output from the control unit 32 is given to the taking lens 21, the image pickup device 24, the signal processing unit 28a, the recording unit 28, the exposure calculation unit 29, the color correction unit 30, and the white balance control unit 31. . A release button 32a is connected to the control unit 32. Here, claim 4 and
The correspondence between the items described in claim 5 and the present embodiment will be described. It should be noted that the correspondence relationship here is one interpretation for reference, and the present invention is not limited to these. First, the optical means described in claims 4 and 5 ,
It corresponds to the taking lens 21. The light flux changing means described in claims 4 and 5 corresponds to the diaphragm 22, the taking lens 21, and the exposure calculation section 29. The imaging means according to claims 4 and 5 ,
It corresponds to the image sensor 24. The color correction means according to claims 4 and 5 comprises a color correction unit 30 and variable gain amplifiers 26a, 26.
Corresponds to b.

FIG. 2 is a flow chart showing the operation of this embodiment. The operation of this embodiment will be described below with reference to FIGS. When the release button 32a is pressed halfway (step S1), the control unit 32 reads the exposure mode set from the outside (step S2).

The photometric unit 29a measures the reflected light of the mirror 23 to obtain the subject brightness (step S3). Further, the colorimetric unit 31a measures the ratio of the tristimulus values of ambient light (step S4).

In this state, if the release button 32a is not fully pressed (step S5), the process returns to step S1 and the above measurement is repeated. When a certain period of time has passed since the release button 32a was released (step S6), the power of the camera is turned off to end the operation.

Here, when the release button 32a is fully pressed (step S5), the control section 32 determines the exposure mode (step S7). If the exposure mode is the "automatic exposure mode", the exposure calculation unit 29 takes in the photometric value of the subject brightness and calculates an appropriate aperture value and exposure period (step S8).

If the exposure mode is the "manual exposure mode", the exposure calculator 29 reads the manually set aperture value (step S9). The color correction unit 30 lowers the gains of the variable gain amplifiers 26a and 26b on the open aperture side in accordance with the aperture value thus determined (step S1).
0).

On the other hand, the white balance control section 31 sets the gains of the variable gain amplifiers 27a and 27b corresponding to the colorimetric values (step S11). In this state, the image sensor 2
The image signal output from the signal No. 4 is variable gain amplifier 26a,
The change in hue due to the aperture value is corrected by 26b, and the white balance is adjusted by the variable gain amplifiers 27a and 27b.

The image signal thus processed is recorded in the recording unit 28 via the signal processing unit 28a (step S12). In this way, in the image pickup apparatus of the present embodiment, the change in hue due to the aperture value is corrected, and an image signal with an accurate hue can be output.

Further, by lowering the gain of the R output, which significantly increases on the open aperture side, it is possible to effectively suppress the hue variation due to the aperture value. Further, by decreasing the gain of the B output which increases on the wide aperture side, it is possible to prevent the phenomenon that the skin color of a person becomes bluish on the wide aperture side.

Next, another embodiment will be described. Figure 3
FIG. 9 is a diagram showing an embodiment corresponding to claims 3 , 4, and 5 . In the figure, the feature of the configuration of the present embodiment is that the colorimetric unit 31
The G output of “a” is directly connected to the white balance control unit 31, and the R output and the B output are respectively transmitted through the white balance control unit 3 via the variable gain amplifiers 40a and 40b.
Connected to 1.

A color correction unit 41 is connected to the control terminals of these variable gain amplifiers 40a and 40b, and an exposure calculation unit 29 and a control unit 32 are connected to the color correction unit 41. In the constituent elements of this figure, the same constituent elements as those of FIG. 1 are designated by the same reference numerals, and description thereof will be omitted. Here, the correspondence relationship between the matters described in claims 4 and 5 and this embodiment will be described. It should be noted that the correspondence relationship here is one interpretation for reference, and the present invention is not limited to these. First, the optical means described in claims 4 and 5 corresponds to the taking lens 21. Claim
The luminous flux changing means described in Nos. 4 and 5 includes a diaphragm 22 and a photographing lens.
21 and the exposure calculation unit 29. Claims 4 and 5
Imaging means according to correspond to the imaging element 24. Claim
The color correction means described in Nos. 4 and 5 includes a color correction unit 30, variable gain amplifiers 27a and 27b, a white balance control unit 31,
And the variable gain amplifiers 40a and 40b.

FIG. 4 is a flow chart showing the operation of this embodiment. The operation of this embodiment will be described below with reference to FIGS. 3 and 4. When the release button 32a is pressed halfway (step S1), the controller 32 reads the exposure mode set from the outside (step S2).

The photometric unit 29a measures the reflected light of the mirror 23 to obtain the subject brightness (step S3). Further, the colorimetric unit 31a measures the ratio of the tristimulus values of ambient light (step S4).

If the release button 32a is not fully pressed (step S5), the process returns to step S1 to repeat the above measurement. When a certain period of time has passed since the release button 32a was released (step S6), the power of the camera is turned off to end the operation.

In this state, when the release button 32a is fully pressed (step S5), the controller 32 determines the exposure mode (step S7). If the exposure mode is the "automatic exposure mode", the exposure calculation unit 29 takes in the photometric value of the subject brightness and calculates an appropriate aperture value and exposure period (step S8).

If the exposure mode is the "manual exposure mode", the exposure calculator 29 reads the manually set aperture value (step S9). The color correction unit 41 increases the gains of the variable gain amplifiers 40a and 40b on the open aperture side in accordance with the aperture value thus determined (step S10).

Therefore, the white balance control section 31
Then, the ratio of the red and blue colorimetric values to be captured becomes large on the open aperture side. In response to such colorimetric values, the white balance control unit 31 controls the variable gain amplifier 27a,
The gain of 27b is reduced on the open aperture side (step S1
1).

Therefore, the image signal output from the image pickup device 24 is adjusted in white balance by the variable gain amplifiers 27a and 27b, and the change in hue due to the aperture value is corrected.

The image signal thus processed is recorded in the recording section 28 via the signal processing section 28a (step S12). In this way, the image pickup apparatus according to the present embodiment can achieve substantially the same effects as those of the above-described embodiments.

Further, in the image pickup apparatus of this embodiment, since the color correction unit 41 corrects the adjustment amount of the white balance control unit 31, the variable gain amplifiers 26a and 26b described above are directly arranged in the signal path of the image signal. You don't have to. Therefore, since the circuit scale of the signal path does not increase, the above-described effect can be enhanced without deteriorating the S / N ratio and the distortion rate of the image signal.

In this embodiment, the color correction unit 41 corrects the colorimetric value by the colorimetric unit 41, but the invention is not limited to this, and the adjustment amount of the white balance control unit 31 may be corrected. For example, the color correction unit 41 uses the variable gain amplifier 27.
The control inputs a and 27b may be corrected. With such a configuration, even when the white balance is manually set and the colorimetric unit 31a is not used, the color correction unit 41 can correct the gains of the variable gain amplifiers 27a and 27b according to the aperture value. .

Although the image pickup apparatus is applied to the electronic still camera in the above-mentioned embodiment, the invention is not limited to this.
It may be applied to a video camera (without a recording device), a video movie camera, and other camera devices.

When the interchangeable photographic lens 21 having a built-in iris is used, the aperture value on the photographic lens 21 side is set to the exposure calculation section 29 or the color correction section 30 on the camera body side via the lens mount portion. , 41.

[0056]

As described above, in the image pickup apparatus according to the first aspect, the ratio of the color stimulus value is corrected according to the aperture value, so that the variation of the hue due to the aperture value is suppressed and the accurate image signal of the hue is obtained. Can be output.

Further, in the image pickup apparatus according to the first aspect , the stimulus value corresponding to red color, which remarkably increases on the wide aperture side, is decreased, so that the fluctuation of the hue can be effectively suppressed. Meanwhile, billing
In the image pickup apparatus of item 2 , since the stimulus value corresponding to blue color that increases on the open aperture side is decreased, it is possible to suppress the hue variation due to the aperture value and output an accurate image signal of the hue.

In the image pickup apparatus of claim 3 , the color correction means is
Since the ratio of the stimulus value of the image signal is corrected through the white balance adjusting means, it is not necessary to separately arrange the variable gain amplifier in the signal path of the image signal. Therefore, it is possible to suppress the hue variation due to the aperture value without deteriorating the S / N ratio and the distortion of the image signal.

As described above, in the image pickup device according to the fourth and fifth aspects , the ratio of the color stimulus values is corrected according to the diameter of the light flux forming the subject image . That is, the image pickup apparatus according to claim 4.
Becomes a red color that increases significantly as the diameter of the luminous flux increases.
Decrease the corresponding stimulus value. On the other hand, the imaging device according to claim 5.
Is equivalent to blue, which increases as the diameter of the light flux increases.
Decrease the stimulation value. As a result, the shooting of claims 4 and 5
In the image device, it is possible to suppress the fluctuation of the hue due to the change of the characteristic of the light flux and to output the image signal of the correct hue.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment corresponding to claims 1, 2 , 4, and 5 .

FIG. 2 is a flow chart showing an operation of an embodiment corresponding to claims 1, 2 , 4, and 5 .

FIG. 3 is a diagram showing an embodiment corresponding to claims 3 , 4, and 5 .

FIG. 4 is a flowchart showing the operation of an embodiment corresponding to claims 3 , 4, and 5 .

FIG. 5 is a sectional view showing an example of a CCD image sensor.

FIG. 6 is a diagram showing an electronic still camera to which a conventional image pickup device is applied.

FIG. 7 is a diagram showing a relationship between an aperture value and an RGB output ratio.

Claims (5)

(57) [Claims] 1. An optical means for forming an optical image of an object, and an opening through which an incident light flux from the optical means passes,
A diaphragm means for adjusting the aperture value by changing the diameter of the opening, an imaging means for converting an optical image formed through the optical means and the diaphragm means into an image signal, and an imaging means for the imaging means. An image pickup apparatus comprising an on-chip microlens arranged on a light receiving side and having a condenser lens formed corresponding to a pixel of the image pickup means, in which an aperture value of the aperture means is captured and corresponding to the aperture value. includes color correction means for correcting the ratio of the color stimulus values of the converted image signal by the image pickup means, the color correction unit, the increase of the diameter of the opening of said throttle means
Therefore, an imaging device characterized by reducing the stimulus value corresponding to red . 2. An optical means for forming an optical image of a subject, and an opening through which an incident light flux from the optical means passes,
A diaphragm means for adjusting the aperture value by changing the diameter of the opening, an imaging means for converting an optical image formed through the optical means and the diaphragm means into an image signal, and an imaging means for the imaging means. An image pickup apparatus comprising an on-chip microlens arranged on a light receiving side and having a condenser lens formed corresponding to a pixel of the image pickup means, in which an aperture value of the aperture means is captured and corresponding to the aperture value. includes color correction means for correcting the ratio of the color stimulus values of the converted image signal by the image pickup means, the color correction unit, the increase of the diameter of the opening of said throttle means
Therefore, an imaging device characterized by reducing the stimulus value corresponding to blue . 3. The image pickup apparatus according to claim 1 , further comprising a white balance adjusting unit that adjusts a white balance of the image signal converted by the image pickup unit, and the color correction unit includes the aperture unit. Corresponding to the aperture value of
An image pickup apparatus which corrects the amount of white balance adjustment by the white balance adjusting means. 4. An optical means for forming an optical image of a subject, a light flux changing means for changing characteristics of a light flux passing through the optical means, and an image forming through the optical means and the light flux changing means. An image pickup means for converting an optical image into an image signal, and a pixel of the image pickup means arranged on the light receiving side of the image pickup means.
On-chip micro with a condensing lens formed corresponding to
In the image pickup apparatus having a lens, corresponding to the characteristic change of the light flux in the light flux changing unit includes a color correcting means for correcting the ratio of the color stimulus values of the converted image signal by the image pickup means, wherein The color correction means increases the red color as the diameter of the luminous flux increases.
An imaging device characterized by reducing a stimulus value corresponding to . 5. Optical means for forming an optical image of a subject, light flux changing means for changing the characteristics of a light flux passing through the optical means, and image formation via the optical means and the light flux changing means. An image pickup means for converting an optical image into an image signal, and a pixel of the image pickup means arranged on the light receiving side of the image pickup means.
On-chip micro with a condensing lens formed corresponding to
In the image pickup apparatus having a lens, corresponding to the characteristic change of the light flux in the light flux changing unit includes a color correcting means for correcting the ratio of the color stimulus values of the converted image signal by the image pickup means, wherein The color correction means increases the blue color as the diameter of the luminous flux increases.
An imaging device characterized by reducing a stimulus value corresponding to .